If we come back to an example with Divine Visitation we will know, that Widespread Brutality would not make an Angel to deal damage to anyone, because you cannot choose it to Amass an Army
First, it created more flexibility, especially for Limited play
Once you know exactly what youre holding, it gets much easier to price it right
Explosive Vegetation and Clash of Wills are good weapons for getting too much mana for Deep-Fiend to matter or keeping an opponents threat off the table, but choosing which key turn to start Deep-Fiending is really tricky, and setting up a multiple-turn sequence in advance with Traverse the Ulvenwald or a reserved Grapple is difficult
Coil and Catch is also a good effect, but Rain of Revelation is hardly playable on its own
Princess Luna could potentially be helpful if it werent for the restrictions put on pulling cards from outside the game